Method for joining dissimilar engine components

ABSTRACT

A method for joining engine components includes positioning a first plurality of thermal protection structures across a thermal protection space between a first thermal protection surface and a second thermal protection surface. The first and second engine components are locally joined by forming a first plurality of transient liquid phase (TLP) or partial transient liquid phase (PTLP) bonds along corresponding ones of the first plurality of thermal protection structures between the first thermal protection surface and the second thermal protection surface. The second thermal protection surface is formed from a second surface material different from a first surface material of the first thermal protection surface.

BACKGROUND

The described subject matter relates generally to combustion engines andmore specifically to methods for joining components for combustionengines.

Combustion engines including internal combustion engines and gas turbineengines such as turbofans, turboshafts, and turboprops provide motivepower in a wide variety of industries and applications. Ground-basedcombustion engines such as internal combustion engines and gas or steamturbines are also used for generating electrical and/or mechanicalpower. Advances in material compositions and processing have led to theuse of more exotic materials in an effort to improve engine efficiency.A more refractory (e.g., more thermally resistant) material could beused to insulate a less refractory material. Thermal-resistanceproperties generally relate to resistance of a substrate to thermallyinduced phase changes.

Since a more refractory material is typically heavier, more expensive,and/or lacking in a key property (e.g., ductility) than less thermallyresistant materials, it would be helpful to use a less refractorymaterial where there is less risk of exposure of that material toextreme conditions. However, there have historically been at least twoissues with this approach. First, there is often a mismatch in thecoefficient of thermal expansion (CTE) between materials. If themismatch is too large, it increases thermally induced strains and therisk of premature failure at the material interface. Second, a suitable,more refractory material may still have a relatively high thermalconductivity, and does not adequately insulate the otherwise suitableless refractory material.

The issues of differential CTE and high thermal conductivity arise,among other places, in the hot section of turbine engines. For example,combustor and turbine components are exposed to hot working gases andthus are often manufactured from combinations of specializedsuperalloys, ceramics, and/or composites. Turbine blades and combustorparts often require vapor or thin film deposition of a metallic bondlayer to form a suitable interface between a less refractory superalloysubstrate and a more refractory ceramic coating. The metallic bond layermediates the different CTEs of the superalloy substrate and ceramiccoating, while also controlling conduction of heat into the superalloysubstrate. Despite a mediating metallic layer, substantial practicallimitations remain on usable combinations of superalloy and/orrefractory ceramic substrates in other applications.

To reduce weight and improve efficiency, it would be helpful to be ableto utilize the best and most cost-effective materials in all parts ofthe engine. This would require a number of dissimilar materials to be inclose proximity to each other. However, each material is likely to havedifferent thermal and mechanical responses. Thus designers must beextremely careful about which materials can be used together, andparticularly about combinations of materials which are to be physicallyjoined or fastened together.

SUMMARY

A method for joining engine components comprises providing a firstengine component with a first thermal protection surface and a secondengine component with a second thermal protection surface. The secondthermal protection surface is formed from a second surface materialdifferent from a first surface material of the first thermal protectionsurface. The first and second thermal protection surfaces are arrangedto have at least one thermal protection space therebetween. A firstplurality of thermal protection structures are positioned across thethermal protection space between the first thermal protection surfaceand the second thermal protection surface. The first engine componentand the second engine component are locally joined by forming a firstplurality of transient liquid phase (TLP) or partial transient liquidphase (PTLP) bonds along corresponding ones of the first plurality ofthermal protection structures between the first thermal protectionsurface and the second thermal protection surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart showing steps of a method for joining enginecomponents formed from dissimilar materials.

FIG. 2A depicts a first combination of the example thermal protectionstructure and transient liquid phase (TLP) or partial transient liquidphase (PTLP) bond.

FIG. 2B depicts a second combination of the example thermal protectionstructure and TLP or PTLP bond.

FIG. 2C depicts a third combination of the example thermal protectionstructure and TLP or PTLP bond.

FIG. 2D depicts a fourth combination of the example thermal protectionstructure and TLP or PTLP bond.

FIG. 3A shows formation of a TLP bond joining a thermal protectionstructure to an adjacent surface.

FIG. 3B shows formation of a PTLP bond joining a thermal protectionstructure to an adjacent surface.

FIG. 4A is a second example thermal protection structure.

FIG. 4B shows example bond locations of the second example thermalprotection structure.

FIG. 5A is a third example thermal protection structure.

FIG. 5B shows example bond locations of the third example thermalprotection structure.

FIG. 6A is a fourth example thermal protection structure.

FIG. 6B shows example bond locations of the fourth example thermalprotection structure.

FIG. 7A is a fifth example thermal protection structure.

FIG. 7B shows example bond locations of the fifth example thermalprotection structure.

FIG. 8A is a sixth example thermal protection structure.

FIG. 8B shows example bond locations of the sixth example thermalprotection structure.

FIG. 9A is a seventh example thermal protection structure.

FIG. 9B shows example bond locations of the seventh example thermalprotection structure.

DETAILED DESCRIPTION

FIG. 1 shows a chart with method 100 for joining engine components withdissimilar materials. Embodiments of method 100 allow for joining ofnumerous combinations of components throughout internal combustionengines, gas and steam turbine engines, among others. By providing ajoining method which minimizes different thermal and mechanicalresponses of each material, it becomes more likely that each componentmaterial can be better optimized. With careful design and selection ofthermal protection structures and transient liquid phase (TLP) orpartial transient liquid phase (PTLP) bonds, numerous combinations ofmetallic, ceramic, and composite components can be joined in a turbineor other combustion engines, which allows increased flexibility instructural material selection, reduced cooling demands, and increasedefficiency. The combination of thermal protection structures and TLP orPTLP bonds can also reduce the number of fasteners, interference fits,or the like, in certain applications as they can provide robust bonds atrelatively low temperatures.

Method 100 is a process for quickly and economically joining a varietyof dissimilar materials in components for combustion engines includinggas turbine engine components. Method 100 begins with steps 102 and 104which respectively include providing first and second engine components.Each of the first and second engine components has respective first andsecond thermal protection surfaces formed from different first andsecond surface materials. The first surface material can have a highermelting point than the second surface material, making the firstmaterial “more refractory”. The use of materials with different meltingpoints or other thermally resistant properties can be done in theinterest of reducing weight and/or cost.

Example classes of materials suitable for the first and second surfacesinclude but are not limited to ceramic materials, metallic materials,ceramic matrix composite (CMC) materials, and metal matrix composite(MMC) materials. Non-limiting examples of suitable ceramic and ceramicmatrix materials can include aluminum oxide (Al₂O₃), silicon nitride(Si₃N₄), silicon carbide (SiC), tungsten carbide (WC), zirconium oxide(ZrO₂), and combinations thereof. Examples of fibers for the CMC and/orMMC materials can include but are not limited to silicon carbide (SiC),titanium carbide (TiC), aluminum oxide (Al₂O₃), carbon (C), andcombinations thereof. Other example fibers for MMC materials can includeboron (B), boron carbide (B₄C), graphite, steel, tungsten (W), andtitanium boride (TiB₂), and combinations thereof. Non-limiting examplesof suitable metals for the metallic materials and/or the metallic matrixmaterials can include aluminum, nickel, iron, titanium, and alloysthereof. As is known in the case of composites, the fibers can be coatedto prevent reaction with the surrounding matrix or to provide additionalcontact area. A number of these materials have favorable thermal andmechanical properties for turbine engine applications.

At step 106, the first and second thermal protection surfaces arearranged in such a way as to have at least one thermal protection spacetherebetween. The thermal protection space can serve a number ofsimultaneous purposes, depending on the relative composition andproperties of the two surface materials. First, a space between thesurfaces may exist where one would not be feasible using other joiningtechniques, thereby reducing weight. In other applications, the thermalprotection space can provide convective and/or impingement cooling toone or both materials. In one example of an engine case, holes could beformed through a less refractory surface, and which direct cooling airthrough the space toward the underside of a more refractory surface. Inother examples, the arrangement could serve as a portion of a path forsecondary air flow or leakage flow.

Step 108 of method 100 includes positioning a plurality of first thermalprotection structures across the thermal protection space between thefirst thermal protection surface and the second thermal protectionsurface. The plurality of first thermal protection structures generallyinclude one or more geometric shapes which, alone or together, bridgethe space between the first and second thermal protection surfaces.

As part of step 110 the first component segment and the second componentsegment can be locally joined by forming a plurality of first TLP orPTLP bonds along corresponding ones of the plurality of first thermalprotection structures between the first thermal protection surface andthe second thermal protection surface. Depending on the degree ofsimilarity or dissimilarity, the thermal protection structures may haveone or more thermal protection elements which are integral to one, both,or neither of the first and second thermal protection surfaces. Thethermal protection elements can additionally or alternatively be joinedvia one or more of the first TLP or PTLP bonds. Example configurationsof TLP or PTLP bonds disposed along a thermal protection element areshown in FIGS. 2A-2D.

It will be recognized that, when referring to TLP bonding, the processcan encompass one or both of a standard TLP bonding process and apartial transient liquid phase (PTLP) bonding process. PTLP bondinggenerally performs better than standard TLP bonding when joining twoceramic materials. References to TLP and/or PTLP bonding, when joining ametallic surface to a non-metallic surface, also include bonds with aretechnically termed active TLP bonds.

A combination of TLP or PTLP bonds along corresponding ones of thethermal protection structures minimize heat transfer by optimizing theconduction paths and empty thermal protection space between the firstand second thermal protection surfaces. This permits the optimization ofdifferent combinations of materials, particularly in previouslyimpractical areas of turbine engines, due to the compliance of thethermal protection structures and design flexibility of the TLP and PTLPbonding processes. Unlike other bonding processes such as sintering,diffusion bonding, etc., TLP and PTLP bonds can be used at or above thebonding temperature. This can prevent damage to the bonding/thermalprotection surfaces and the components being joined.

Optional step 112 includes positioning a plurality of second thermalprotection structures across the thermal protection space between thefirst thermal protection surface and the second thermal protectionsurface. In conjunction with step 112, optional step 114 describeslocally joining the first component segment and the second componentsegment by forming a plurality of second TLP or PTLP bonds alongcorresponding ones of the plurality of second thermal protectionstructures.

Using different geometries of thermal protection structures allowsorganization of different (e.g. first and second) thermal protectionstructures according to localized thermal gradients, hot spots, or thelike. First and second geometries can be combined and used to reinforcehigh stress areas or to avoid high strain areas of one or both materialsbeing joined. Thus the different thermal protection structures can begraded, arranged transversely to one another, or may be placed indiscrete or localized regions of the thermal protection surfaces.Example geometries are shown and described with respect to FIGS. 4A-9B.

FIGS. 2A-2D show various configurations of first engine component 200being joined to second engine component 202. First engine component 200has first thermal protection surface 204 formed from a first surfacematerial, and second engine component 202 has second thermal protectionsurface 206 formed from a second surface material different from thefirst surface material. Thermal protection space 208 is disposed betweenfirst and second thermal protection surfaces 204, 206. Theseconfigurations are representative of method 100 in which thermalprotection structures and TLP or PTLP bonds are formed between thermalprotection surfaces. It should be noted that in FIGS. 2A-2D, thedimensions of bonds 214A, 214B are exaggerated for clarity.

Typically, the first surface material can have a higher melting pointthan the second surface material, making first thermal protectionsurface 204 “more refractory” than second thermal protection surface206. As a result there is substantial risk of mismatched thermal growthand/or thermal conduction when joining first surface 204 directly tosecond surface 206. Thus in FIG. 2A, first and second surfaces 204, 206are spaced apart and space 208 is bridged with thermal protectionstructures 210A. Each structure 210A includes a single (e.g., first)thermal protection element 212A projecting from first thermal protectionsurface 204 into thermal protection space 208. TLP or PTLP bond 214A isthen formed along distal edge 216A of each thermal protection structure210A and second surface 206 to locally join surfaces 204 and 206 acrossthermal protection space 208.

FIG. 2B shows a similar configuration to FIG. 2A. The difference in FIG.2B is that second thermal protection element 212B projects from secondthermal protection surface 206 into thermal protection space 208 to formthermal protection structures 210B. In this instance a TLP or PTLP bond214B is then formed along each distal edge 216B of thermal protectionstructures 210B and first surface 204, thereby locally joining first andsecond thermal protection surfaces 204 and 206 across thermal protectionspace 208.

In FIG. 2C, thermal protection structures 210C are defined by acombination of first thermal protection elements 212A and second thermalprotection elements 212B. First and second thermal protection elements212A, 212B each project from respective first and second thermalprotection surfaces 204, 206 partially into thermal protection space208. A TLP or PTLP bond 214A can then be added at each interface ofdistal edges 216A, 216B so that when second thermal protection elements212B are properly aligned with first elements 212A, the bonded pair ofopposed thermal protection elements define thermal protection structure210C across space 208.

In certain embodiments, such as in the examples of FIGS. 2A-2C, one orboth thermal protection elements 212A, 212B can be integrally formedwith corresponding first and second thermal protection surfaces 204,206. This can be done, for example, when thermal conductivity betweenengine component(s) 200, 202 is less of a concern and/or when materialsof surfaces 204, 206 have compatible CTE values. In these embodiments,integration of first and/or second thermal protection elements 212A,212B can be readily incorporated into the production of enginecomponent(s) 200, 202, such as by casting or additive manufacturing.

FIG. 2D shows an alternative arrangement in which thermal protectionstructures 210D are joined to first and second thermal protectionsurface 204, 206 by TLP or PTLP bonds 214A and 214B. In other words,thermal protection structures 210D include separately formed thermalprotection elements 212C which have respective TLP or PTLP bonds 214A,214B joining first and second thermal protection surfaces 204, 206 toedges 218A, 218B of thermal protection elements 212C.

In certain embodiments, thermal protection structures 210A-210D can bemade from the same material as one of the first and second thermalprotection surfaces 204, 206. Examples are described with reference toFIG. 1 above. In certain alternative embodiments, such as those shown inFIG. 2D, thermal protection structures 210D can be made from a thirdmaterial which has different composition from the materials of first andsecond thermal protection surfaces 204, 206. The third material can beless refractory than the first material and more refractory than thesecond material. It can additionally or alternatively have a lowerthermal conductivity (i.e., be thermally insulating) relative to one orboth of the first and second materials.

The third material of thermal protection structures 210D can, forexample, be a compliant bridging material. In an example of joining twodifferent ceramic surfaces (either monolithic ceramics or matrix bindersof CMC materials), the compliant bridging material can be a thirdceramic which is compatible with the TLP or PTLP bonding process,examples of which is shown in FIGS. 3A and 3B.

One or more of the configurations shown in FIGS. 2A-2D can be combinedin the same joining region. For example, first engine component 200 canbe joined to second engine component 202 using alternating instances orrows of two or more thermal protection structures 210A-210D so as topotentially enhance the overall bonding strength, and/or simplify theformation of the total number of TLP and/or PTLP bonds.

FIGS. 3A and 3B respectively show a TLP bond and a PTLP bond joining athermal protection element to an adjacent surface, such as is describedin steps 110/114 of method 100. In these embodiments, standard TLP bondstypically work best for joining metallic materials while PTLP bondstypically work best for joining non-metallic materials (e.g., monolithicceramic or ceramic matrix composite).

FIG. 3A depicts a standard TLP bond setup before joining thermalprotection element 312 to adjacent bonding structure 326. Adjacentbonding structure 326 can include, for example, one of thermalprotection surfaces 204, 206 shown in FIG. 2A, 2B, or 2D. Alternatively,adjacent bonding structure 326 can include a surface of a second thermalprotection element such as element 212B depicted in FIG. 2C.

Standard TLP bonds include interlayer 330 which is diffused into the twobonding surfaces (surfaces 332 and 334 in FIG. 3A). TLP interlayer 330begins as a foil, powder, braze paste, or other suitable format forapplying the metallic material (e.g., electroplating or PVD). Pressurecan be applied to the TLP bond setup along with heat to raise thetemperature of the TLP bond assembly. The bonding temperature is abovethe original melting point of interlayer 330 before formation of the TLPbond.

When performing the TLP process, solid TLP interlayer 330 begins todiffuse into the substrate materials 312, 326 and then melts on reachinga suitable temperature. This temperature is either the direct meltingpoint of interlayer 330 or, for each interface, it is the eutecticmelting point of interlayer 330 and the respective substrate (e.g., 312or 326). This causes a degree of meltback into substrates 312, 326 asequilibrium is attained. To control excessive meltback, TLP interlayer330 can be provided with a similar composition to one of the substratesand/or can have a eutectic composition. After a sufficient bonding time,the liquefied interlayer 330 isothermally solidifies at the bondingtemperature to form a standard TLP bond (e.g., bonds 214A, 214B shown inFIGS. 2A-2D). Optional homogenization of the TLP bond serves to furtherdiffuse material into substrates 312, 326, and can increase the meltingtemperature of the resulting TLP bond.

FIG. 3B is an alternate bonding arrangement for thermal protectionelement 312 joined to adjacent bonding structure 326. To bondnon-metallic substrates, FIG. 3B shows a PTLP bond setup with interlayer331 which can include first layer 336, second layer 338, and refractorylayer 340. Layers 336, 338 are shown as individual layers, but one orboth layers 336, 338 can alternatively comprise multiple layers.Refractory layer 340 can be, for example, nickel or an alloy thereof.Alternative examples of suitable metals for refractory layer 340 includegold, cobalt, copper, niobium, palladium, platinum, silicon, tantalum,titanium, vanadium, and alloys thereof. Layers 336, 338 are selected soas to wet the ceramic substrates (here, surfaces 332, 334 when the bondassembly is heated to the bonding temperature. As layers 336, 338 areheated, they cause a controlled degree of meltback to refractory layer340 while also wetting the adjacent ceramic surfaces 332, 334. Thiswetting can be caused directly by layers 336, 338 or by alloys formed oneach side of the bond between layer 336 or 338 and refractory layer 340,respectively. The bond assembly can then be maintained at a bondingtemperature for a suitable time so as to isothermally solidify andoptionally homogenize the bonding materials into the interlayer.

In addition to joining two different components, a hybrid component madeof dissimilar materials can also be produced via TLP bonding of one ormore thermal protection structures. A space is left between thematerials to minimize thermal conduction and/or provide cooling of themore refractory component. The combination of a hybrid design andthermal protection structures allow for complex geometries at areasonable cost.

The remaining figures show various suitable geometries for thermalprotection structures and hybrid components formed according to thepreceding description.

FIGS. 4A and 4B show an array of first thermal protection structures 410extending through thermal protection space 408 between first enginecomponent 400 and second engine component 402. In FIG. 4A, an irregulararray of thermal protection elements 412 having a polygonalcross-section are secured to, or are integrally formed with, firstthermal protection surface 404. In this example, FIG. 4B showsrectangular thermal protection elements 412 while TLP or PTLP bonds414A, 414B join edges 418A, 418B of thermal protection elements 412 torespective thermal protection surfaces 404, 406.

FIGS. 5A and 5B show an array of first thermal protection structures 510extending through thermal protection space 508 between first enginecomponent 500 and second engine component 502. In FIG. 5A, a regulararray of thermal protection elements 512 having a round or curvedcross-section are secured to, or are integrally formed with, firstthermal protection surface 504 of first engine component 500. In thisexample, FIG. 5B shows circular thermal protection elements 512 with TLPor PTLP bonds 514A, 514B joining edges 518A, 518B of thermal protectionelements 512 to respective thermal protection surfaces 504, 506.

FIGS. 5A and 5B show similar arrays of first thermal protectionstructures having a rounded (circular, oval, etc.) cross-section. Thearray of protrusions can be of any cross-sectional shape, and can eitherbe arranged in a regular grid (FIG. 5A) or an offset grid (FIG. 4A). Theplurality of individual protrusions can extend generally normal to atleast one of the first thermal protection surface and the second thermalprotection surface. It will be appreciated that any regular, irregular,or random pattern of protrusions can be used, for example, to addresshot spots, areas of potential fatigue or weakness or the like.

In certain embodiments, a second plurality of thermal protectionstructures is also positioned across the thermal protection spacebetween the first and second thermal protection surfaces.

A first example of an assembly with multiple thermal protectionstructures is shown in FIGS. 6A-6B in which a plurality of corrugatedribs 612A serve as first thermal protection structures 610A acrossthermal protection space 608 between first engine component 600 andsecond engine component 602. First TLP or PTLP bonds 614A, 614B aredisposed along first thermal protection structures 610A to locally joinfirst thermal protection surface 604 and second thermal protectionsurface 606

FIGS. 6A and 6B also show a set of second, longitudinal ribs 612Barranged transversely to corrugated ribs 612A. A corresponding group ofTLP or PTLP bonds 642A, 642B also locally join thermal protectionsurfaces 604, 606. In the absence of longitudinal ribs 612B, corrugatedribs 612A can define longitudinal passages along space 608.

In FIGS. 7A and 7B, first thermal protection structures 710A, 710B alsohave a plurality of corrugated ribs 712A, 712B serving as first thermalprotection structures 710A across thermal protection space 708 betweenfirst engine component 700 and second engine component 702. As in FIGS.6A and 6B, first TLP or PTLP bonds 714A, 714B are disposed along firstthermal protection structures 710A to locally join first thermalprotection surface 704 and second thermal protection surface 706.

In place of the longitudinal transverse ribs, FIG. 7A shows a set ofsecond corrugated ribs 712B arranged transversely to first corrugatedribs 712A. FIG. 7B illustrates how both sets of ribs 712A, 712B can bedisposed across thermal protection space 708 between first enginecomponent 700 and second engine component 702. Second TLP or PTLP bonds742A, 742B are formed along respective corresponding ones of the firstand second thermal protection structures 710A, 710B to locally jointhermal protection surfaces 704, 706.

It will be appreciated that, with respect to FIGS. 6A-7B not all of thethermal protection structures are required to be ribs. For example, someor all of the ribs can be replaced by isolated projections as shown inFIGS. 4A-5B.

The final two non-limiting examples are shown in FIGS. 8A-9B. In FIGS.8A-8B, a plurality of first thermal protection structures 810 include aninterconnected grid of repeating polygonal shapes extending across space808, between first and second thermal protection surfaces 804, 806 ofrespective first and second engine components 900, 902. In FIG. 8A, agrid of ribs 812 are arranged into interlocking hexagonal shapes.Alternatively, ribs 812 can be arranged so that the hexagons arereplaced with a rectangular grid or a triangular isogrid. TLP or PTLPbonds 814A, 814B complete connection of first and second components 800,802.

FIGS. 9A-9B shows an irregular grid arrangement of transversely arrangedthermal protection structures 910 connecting first and second enginecomponents 900, 902. First ribs 912A extend longitudinally along space908 between thermal protection surfaces 904, 906, while second ribsegments 912B are arranged in an irregular manner transversely to firstrib segments 912A. First TLP or PTLP bonds 914A, 914B secure ribs 912Ain place, while second TLP or PTLP bonds 942A, 942B secure transverseribs 912B.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A method for joining engine components comprises providing a firstengine component with a first thermal protection surface and a secondengine component with a second thermal protection surface. The secondthermal protection surface is formed from a second surface materialdifferent from a first surface material of the first thermal protectionsurface. The first and second thermal protection surfaces are arrangedto have at least one thermal protection space therebetween. A firstplurality of thermal protection structures are positioned across thethermal protection space between the first thermal protection surfaceand the second thermal protection surface. The first engine componentand the second engine component are locally joined by forming a firstplurality of transient liquid phase (TLP) or partial transient liquidphase (PTLP) bonds along corresponding ones of the first plurality ofthermal protection structures between the first thermal protectionsurface and the second thermal protection surface.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

A method for joining engine components according to an exemplaryembodiment of this disclosure, among other possible things includesproviding a first engine component including a first thermal protectionsurface formed from a first surface material; providing a second enginecomponent including a second thermal protection surface formed from asecond surface material different from the first surface material;arranging the first and second thermal protection surfaces to have atleast one thermal protection space therebetween; positioning a pluralityof first thermal protection structures across the thermal protectionspace between the first thermal protection surface and the secondthermal protection surface; and locally joining the first enginecomponent and the second engine component by forming a plurality offirst transient liquid phase (TLP) or partial transient liquid phase(PTLP) bonds along corresponding ones of the plurality of first thermalprotection structures between the first thermal protection surface andthe second thermal protection surface.

A further embodiment of the foregoing method, wherein at least one ofthe first surface material and the second surface material is selectedfrom one of: a ceramic material, a metallic material, a ceramic matrixcomposite (CMC) material, and a metal matrix composite (MMC) material.

A further embodiment of any of the foregoing methods, wherein theceramic material comprises one or more of: aluminum oxide (Al₂O₃),silicon nitride (Si₃N₄), silicon carbide (SiC), tungsten carbide (WC),and zirconium oxide (ZrO₂).

A further embodiment of any of the foregoing methods, wherein the CMCmaterial comprises a plurality of fibers selected from one or more of:silicon carbide (SiC), titanium carbide (TiC), aluminum oxide (Al₂O₃),and carbon (C).

A further embodiment of any of the foregoing methods, wherein the CMCmaterial comprises a ceramic matrix selected from one or more of:aluminum oxide (Al₂O₃), silicon nitride (Si₃N₄), and silicon carbide(SiC).

A further embodiment of any of the foregoing methods, wherein the MMCmaterial comprises a plurality of fibers selected from one or more of:silicon carbide (SiC), titanium carbide (TiC), aluminum oxide (Al₂O₃),carbon (C), boron (B), boron carbide (B₄C), graphite, steel, tungsten(W), and titanium boride (TiB₂).

A further embodiment of any of the foregoing methods, wherein at leastone of the first engine component and the second engine component is aturbine engine component.

A further embodiment of any of the foregoing methods, wherein theturbine engine component is a hot section component.

A further embodiment of any of the foregoing methods, wherein at leastone of the first thermal protection structures comprises: a firstthermal protection element projecting from the first thermal protectionsurface into the thermal protection space.

A further embodiment of any of the foregoing methods, wherein the firstthermal protection element is integrally formed with the first enginecomponent.

A further embodiment of any of the foregoing methods, wherein the firstthermal protection element is joined to the first engine component by atleast one of the plurality of first TLP or PTLP bonds.

A further embodiment of any of the foregoing methods, wherein at leastone of the first thermal protection structures further comprises: asecond thermal protection element projecting from the second thermalprotection surface into the thermal protection space, the second thermalprotection element aligned with the first thermal protection element todefine a thermal protection structure having a pair of opposed thermalprotection elements.

A further embodiment of any of the foregoing methods, wherein the secondthermal protection element is integrally formed with the second enginecomponent.

A further embodiment of any of the foregoing methods, furthercomprising: joining the second thermal protection element to the secondengine component by at least one of the plurality of first TLP or PTLPbonds.

A further embodiment of any of the foregoing methods, furthercomprising: joining the second thermal protection element to the firstthermal protection element by at least one of the plurality of first TLPor PTLP bonds.

A further embodiment of any of the foregoing methods, wherein at leastone of first thermal protection structures comprises a plurality ofindividual protrusions extending generally normal to at least one of thefirst thermal protection surface and the second thermal protectionsurface.

A further embodiment of any of the foregoing methods, wherein theplurality of first thermal protection structures comprises a pluralityof corrugated ribs extending between the first thermal protectionsurface and the second thermal protection surface.

A further embodiment of any of the foregoing methods, wherein theplurality of first thermal protection structures comprises an irregulargrid of ribs extending between the first thermal protection surface andthe second thermal protection surface.

A further embodiment of any of the foregoing methods, wherein theplurality of first thermal protection structures comprises aninterconnected grid of repeating polygon shapes extending between thefirst thermal protection surface and the second thermal protectionsurface.

A further embodiment of any of the foregoing methods, wherein theplurality of first thermal protection structures comprises aninterconnected grid of repeating geometric shapes extending between thefirst thermal protection surface and the second thermal protectionsurface.

A further embodiment of any of the foregoing methods, furthercomprising: positioning a plurality of second thermal protectionstructures across the thermal protection space between the first thermalprotection surface and the second thermal protection surface; andlocally joining the first engine component and the second enginecomponent by forming a plurality of second transient liquid phase (TLP)bonds along corresponding ones of the plurality of second thermalprotection structures between the first thermal protection surface andthe second thermal protection surface.

A further embodiment of any of the foregoing methods, wherein thepositioning step comprises: arranging the plurality of second thermalprotection structures transversely to at least some of the firstplurality of thermal protection structures.

A further embodiment of any of the foregoing methods, wherein theplurality of second thermal protection structures comprises a pluralityof ribs extending between the first thermal protection surface and thesecond thermal protection surface.

A further embodiment of any of the foregoing methods, wherein theplurality of ribs are corrugated.

A further embodiment comprising an engine component formed according toany of the preceding embodiments.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

The invention claimed is:
 1. A method for joining engine components, themethod comprising: providing a first engine component including a firstthermal protection surface formed from a first surface material;providing a second engine component including a second thermalprotection surface formed from a second surface material different fromthe first surface material; arranging the first and second thermalprotection surfaces to have at least one thermal protection spacetherebetween; positioning a plurality of first thermal protectionstructures across the thermal protection space between the first thermalprotection surface and the second thermal protection surface; andlocally joining the first engine component and the second enginecomponent by forming a plurality of first transient liquid phase (TLP)or partial transient liquid phase (PTLP) bonds along corresponding onesof the plurality of first thermal protection structures between thefirst thermal protection surface and the second thermal protectionsurface.
 2. The method of claim 1, wherein at least one of the firstsurface material and the second surface material is selected from oneof: a ceramic material, a metallic material, a ceramic matrix composite(CMC) material, and a metal matrix composite (MMC) material.
 3. Themethod of claim 2, wherein the ceramic material comprises one or moreof: aluminum oxide (Al₂O₃), silicon nitride (Si₃N₄), silicon carbide(SiC), tungsten carbide (WC), and zirconium oxide (ZrO₂).
 4. The methodof claim 2, wherein the CMC material comprises a plurality of fibersselected from one or more of: silicon carbide (SiC), titanium carbide(TiC), aluminum oxide (Al₂O₃), and carbon (C).
 5. The method of claim 2,wherein the CMC material comprises a ceramic matrix selected from one ormore of: aluminum oxide (Al₂O₃), silicon nitride (Si₃N₄), and siliconcarbide (SiC).
 6. The method of claim 2, wherein the MMC materialcomprises a plurality of fibers selected from one or more of: siliconcarbide (SiC), titanium carbide (TiC), aluminum oxide (Al₂O₃), carbon(C), boron (B), boron carbide (B₄C), graphite, steel, tungsten (W), andtitanium boride (TiB₂).
 7. The method of claim 1, wherein at least oneof the first engine component and the second engine component is aturbine engine component.
 8. The method of claim 7, wherein the turbineengine component is a hot section component.
 9. The method of claim 1,wherein at least one of the first thermal protection structurescomprises: a first thermal protection element projecting from the firstthermal protection surface into the thermal protection space.
 10. Themethod of claim 9, wherein the first thermal protection element isintegrally formed with the first engine component.
 11. The method ofclaim 9, wherein the first thermal protection element is joined to thefirst engine component by at least one of the plurality of first TLP orPTLP bonds.
 12. The method of claim 9, wherein at least one of the firstthermal protection structures further comprises: a second thermalprotection element projecting from the second thermal protection surfaceinto the thermal protection space, the second thermal protection elementaligned with the first thermal protection element to define a thermalprotection structure having a pair of opposed thermal protectionelements.
 13. The method of claim 12, wherein the second thermalprotection element is integrally formed with the second enginecomponent.
 14. The method of claim 12, further comprising: joining thesecond thermal protection element to the second engine component by atleast one of the plurality of first TLP or PTLP bonds.
 15. The method ofclaim 12, further comprising: joining the second thermal protectionelement to the first thermal protection element by at least one of theplurality of first TLP or PTLP bonds.
 16. The method of claim 1, whereinat least one of first thermal protection structures comprises aplurality of individual protrusions extending generally normal to atleast one of the first thermal protection surface and the second thermalprotection surface.
 17. The method of claim 1, wherein the plurality offirst thermal protection structures comprises a plurality of corrugatedribs extending between the first thermal protection surface and thesecond thermal protection surface.
 18. The method of claim 1, whereinthe plurality of first thermal protection structures comprises anirregular grid of ribs extending between the first thermal protectionsurface and the second thermal protection surface.
 19. The method ofclaim 1, wherein the plurality of first thermal protection structurescomprises an interconnected grid of repeating polygon shapes extendingbetween the first thermal protection surface and the second thermalprotection surface.
 20. The method of claim 1, wherein the plurality offirst thermal protection structures comprises an interconnected grid ofrepeating geometric shapes extending between the first thermalprotection surface and the second thermal protection surface.
 21. Themethod of claim 1, further comprising: positioning a plurality of secondthermal protection structures across the thermal protection spacebetween the first thermal protection surface and the second thermalprotection surface; and locally joining the first engine component andthe second engine component by forming a plurality of second transientliquid phase (TLP) bonds along corresponding ones of the plurality ofsecond thermal protection structures between the first thermalprotection surface and the second thermal protection surface.
 22. Themethod of claim 21, wherein the positioning step comprises: arrangingthe plurality of second thermal protection structures transversely to atleast some of the first plurality of thermal protection structures. 23.The method of claim 21, wherein the plurality of second thermalprotection structures comprises a plurality of ribs extending betweenthe first thermal protection surface and the second thermal protectionsurface.
 24. The method of claim 23, wherein the plurality of ribs arecorrugated.